Behavioral genetics

Behavioral genetics is a major field of genetics which studies the nature and origins of individual differences in behavior, relying on statistics to gain insight into the difference between nature and nurture, and the genetics behind unusual traits.

Studies
Behavioral genetics is an incredibly difficult field of study which seeks to determine the degree upon which a behavioral trait is influenced by genetics. It is hard to do controlled experiments in human populations, so research relies heavily on inbred animal studies and twin studies for the data that is interpreted. In inbred animal studies, scientists can create a strain of mice that is genetically highly inbred, making them homozygous at almost all their loci. Researchers can also do behavioral experiments to determine how these inbred animals respond to different situations such as maze running. Maze running can show how inbred mice run a learning maze, and scientists can breed fast-running mice and slow-running mice by selective breeding, in addition to  determining the degree of "heritability" (the portion of the variance that is the contribution of genetics to the trait). Heritability ranges from 1 (totally influenced by genetics) to 0 (totally influenced by the environment). Interestingly, separated twins often have remarkably similar IQs, disease risks, behavioral trait risks, favorite colors, and other traits, showing high heritability. As twins mature, the controls over the actual expression of the genes they inherit can change over time. Environmental influences like diet and smoking can alter gene expression a great deal, and this can have a significant effect on the phenotypes of even monozygotic twins.